This five-year study proposes to examine and evaluate the process of treatment service delivery with a special focus on the roles and functions of drug treatment counselors. The study will have two related but distinctive components. The first component is a survey of all counselors in 40 treatment programs selected in Los Angeles County and a record abstraction of these counselors' clients who entered the program within the past 12 months. The 40 treatment programs will include five modalities (e.g., outpatient drug free programs, residential or therapeutic community programs, methadone maintenance outpatient programs, hospital inpatient programs, and day treatment programs) for which program level information (e.g., policy, philosophy, staffing, service provision, etc.) are currently being collected in a treatment survey conducted by the PI. Together with interviews of program directors and treatment survey data, these data (e.g., counselor survey and client record abstraction will provide comprehensive information at program, counselor, and client levels. A set of multilevel analyses (e.g., Hierarchical Linear Models) will be applied to these hierarchical data to assess client outcome (e.g., treatment retention) as functions of multilevel influences including program, counselor, and client variation. The second component of the study is a prospective, longitudinal substudy which includes a smaller set of counselors and their clients for in-depth face-to-face interviews. Clients will be interviewed again six months after the initial contact. This substudy is designed to obtain detailed measures on the counselor-client therapeutic relationship and on relevant multiple outcomes. The selection criteria of counselors will be determined by the results from the first component of the study (e.g., the counselor survey and retrospective counselor evaluation). Particular attention will be paid to dimensions that suggest effective practices or approaches that can be incorporated into counselor training programs. A computerized system will be developed to establish the database and to provide timely data analysis. Extensive statistical analyses and model applications will be performed. The study will enhance knowledge about the current roles and functions of drug treatment counselors in the treatment system, identify determinants of effective counselors, and contribute to improved client outcomes by identifying counselor characteristics that will be useful in matching clients to appropriate treatment. The multilevel data collection and analysis should lead to important breakthroughs in the study of client outcomes in relation to program, counselor, and client characteristics.